The present invention is related to a Lorentz force-driven resonator, such as a xylophone bar magnetometer (XBM), based mechanical mixer/filter for radio frequency (RF) applications. More specifically, the present invention is related to an array of Lorentz force-driven mechanical filter/mixers for use in channelized RF receiver applications.
The Johns Hopkins University Applied Physics Laboratory has patented a novel device capable of high frequency magnetic field measurement, the xylophone bar magnetometer of U.S. Pat. No. 5,959,452, which makes use of the Lorentz force generated by a current in a magnetic field. Two principle advantages of the Lorentz force-driven resonant device over other mechanical designs are its ability to function as both a filter and mixer/downconverter and its implementation as a micro electromechanical system (MEMS) design.
There is increasing interest in the development of miniature, high frequency narrow band filters to replace existing filters in RF applications. The trend is constantly toward smaller size, lower power consumption, and lower cost for similar performance. Existing high frequency, narrow band filters are based on large, superconducting systems or utilize multiple electronic filter stages. The Lorentz force-driven mechanical resonator described herein can be used as a filter and a mixer to process signals over a broad range of frequencies.
The present invention is a mechanical mixer/filter apparatus that is rooted in a resonator design described in commonly owned U.S. Pat. No. 5,959,452 which is incorporated herein by reference. The present invention also includes a system in which an integrated array of micro-fabricated, electromechanical mixer/filters may be used, inter alia, in channelized RF receiver applications.
The present invention is based on the Lorentz force-driven resonating bar magnetometer that utilizes a high Q resonant structure as both a mixing device and a high-Q bandpass filter. Specifically, an external time varying magnetic field (B) may be applied to the device while simultaneously running a time varying electrical current (I) through the device. The resulting Lorentz force (Ixc3x97B) is proportional to the vector product of the electrical current in the bar and the external magnetic field. By adjusting the frequencies of the current and external magnetic field, the Lorentz force can be controlled to cause the bar to vibrate at its resonant frequency.
Integrating a Lorentz force-driven mechanical resonator with a magnetic field coil produces the functionality of an ideal RF mixer coupled with a high-Q intermediate frequency (IF) filter. Furthermore, a Lorentz force-driven mechanical resonator mixer/filter can operate in mixing mode at frequencies into the GHz range making it useful for UHF and VHF applications. This includes, but is not limited to, cellular and wireless applications, particularly those in which space, weight and power are considerations. Each of the Lorentz force-driven mechanical resonator designs presented herein may also be arrayed for use in channelized RF applications.